Hydraulic jack arrangement for the steering mechanism of a vehicle

ABSTRACT

A hydraulic piston and cylinder device which permits automatic adjustment of the length of a coupling bar for the two crank arms of the steering pivot of a four-wheeled vehicle as a function of the angles of pivoting of these wheels. This device permits very large angles of pivoting for the inside wheel on the turn and good operation of the steering system.

United States Patent Bobard 5] Oct. 16, 1973 [54] HYDRAULIC JACKARRANGEMENT FOR 2,111,668 3/1938 Latzen 280/87 B THE ST MECHANISM OF A2,173,419 9/1939 Johnson.... 280/80 VEHICLE 3,291,245 12/1966 l-lewko180/792 Inventor: Emile Bobard, 17 Rue de Reon,

Beaune, France Filed: Mar. 10, 1971 Appl. No.: 122,669

Related US. Application Data Continuation-in-part of Ser. No. 783,306,Dec. 12,

1968, abandoned.

US. Cl 280/95 R, 280/87 B Int. Cl 862d 7/06 Field of Search 280/95, 90,34 R,

References Cited UNITED STATES PATENTS Weiss 280/87 B FOREIGN PATENTS ORAPPLICATIONS 853,578 11/1960 Great Britain 280/95 PrimaryExaminer-Kenneth l-l. Betts Attorney-Wilkinson, Mawhinney & Theibault[57] ABSTRACT A hydraulic piston and cylinder device which permitsautomatic adjustment of the length of a coupling bar for the two crankarms of the steering pivot of a fourwheeled vehicle as a function of theangles of pivoting of these wheels. This device permits very largeangles of pivoting for the inside wheel on the turn and good operationof the steering system.

8 Claims, 9 Drawing Figures Patented Oct. 16, 1973 3,765,697

3 She ets-Sheet 1 Patented Oct. 16, 1973 3,765,697

3 Sheets-Sheet 2 Patented Oct. 16, 1973 3 Sheets-Sheet 3 Thisapplication is a continuation-in-part application of applicantsapplication Ser. No. 783,306 filed Dec.

12, 1968 now abandoned, for A HYDRAULIC JACK ARRANGEMENT ALLOWINGADJUSTMENT PARTICULARLY OF A VEHICLE STEERING LINKAGE ELEMENT.

The present invention is directed to an improved steering linkage devicefor a vehicle having a front set of steering wheels, such devicepremitting remarkably great turning angles, even when the longitudinalwheelbase of the vehicle is of the order of the width of its tread, asis the case for certain agricultural tractors.

It is known in the art that the steering devices of usual self-propelledfour-wheeled vehicles comprise, mainly for the control of the pivotingof their two steering wheels, crank arms whose axes converge practicallyin the centre of the distance between the rear wheels, when the twosteering wheels are arranged parallel to each other and to the rearwheels in order to be driven in a straight line.

However, the above conventional arrangement does not permit relativelysmall pivotings which are necessary for the work of certain tractorsbecause, for such angles, the position of the crank arm of the wheelsituated on the inside of the turn with respect to the conventionalcoupling bar of the crank arms is too close to the neutral position toguarantee the safe pivoting of the inside wheel.

In addition, these angles formed by the crank arm of the inside steeringwheel on a turn and the coupling bar are even smaller since thewheelbase of the longitudinal wheels is itself smaller in comparisonwith the width of the tread of the vehicle.

Steering links of known'tractors have already been equipped with twocoupling bars arranged obliquely with respect to the transversedirection of the frame in order to permit pivoting angles which arenotably greater than with a single coupling bar. However, the twocoupling bars must be associated with each other on a median support,rigid with the frame and generally offset to the front of the latterwhich creates a bulkiness often unacceptable and of difficultmaintenance of this support in the centre of the two wheel pivots if theframe is of adjustable width.

The present invention is intended to overcome these drawbacks.

An object of the present invention is directed to an improved steeringlinkage device comprising a single bar for coupling two crank arms ofthe pivots of steering wheels and applicable to the front set ofsteering wheels of a four-wheeled vehicle.

Another object of the invention is to provide a linkage device of thetype described above, permitting relatively large pivoting angles of thewheels of a front steering set, such pivoting angles being able toreach. with ease a value of 90.

A further object of the invention is to put forward a linkage device ofthe above type, permitting the angles formed by the crank arms of thesteering wheel pivots and the bar to be large enough to ensure safeoperation of the linkage, even for large pivoting angles.

A still further object of the invention is to provide an improvedsteering linkage device of the above type, capable of equipping avehicle having a relatively short and relatively wide frame, to permitrelatively large angles of pivoting and safe operation of the linkage.

Another object of the invention is to provide a simple linkage devicewhich is inexpensive, easy to implement and to mount on a vehicle of thetype mentioned above.

With the foregoing and other objects in view, the invention will be morefully described hereinafter, and will be more particularly pointed outin the claims appended hereto.

In the drawings, wherein like symbols refer to like or correspondingparts throughout the several views:

FIG. 1 shows diagrammatically in plan view, a fourwheeled vehicleequipped with a steering linkage according to the invention;

FIG. 2 shows in side elevation the linkage device of FIG. 1;

FIG. 3 shows on a larger scale an element of the device of FIGS. 1 and2;

FIGS. 4 to 6 are diagrams permitting of explaining the advantages of thedevice of FIGS. 1 and 2; and

FIGS. 7, 8a and 8b show diagrammatically in plan view, an alternativeform of the device of FIGS. 1 and 2.

Shown in FIGS. 1 thru 3 are the outlines of two wheels 1d, 1g arrangedin the usual form of a wheel set and in the alignment of two otherwheels 2d, 2g which likewise form another wheel set.

These wheels 1d to 2g are of the type on conventional self-propelledvehicles and these two wheel sets constitute respectively the front andrear wheel sets bearing a frame of a self-propelled vehicle, the framenot being shown for clarity of the FIG. 1.

Each wheel 1d, lg is mounted in a conventional manner on a spindle (notshown), which spindle is rigid with a pivot 3d (3g)'articulated on thevehicle frame and equipped with a crank arm 4d (4g) to form aconventional steering linkage element of the vehicle.

A bar 5 is connected in a usual manner by one of its ends to the crankarm 4a, the other end of bar 5 being rigid with the base of a cylinderformed for the sliding of a piston 6p and of the ram 7 of the latter,the end of the ram 7 being also articulated to the other crank arm 4g.The bar 5 and the ram 7 constitute a coupling bar 5-7 for the crank arms4d, 4g, the length of this bar 5-7 being adjustable by a first cylinder60 with piston or ram 6p as will be set forth hereinafter. One of thetie-rod (not shown); this tie-rod being controlled by a usual steeringdevice comprising a column and its steering-wheel (not shown).

A second cylinder and ram unit 8 comprises a cylinder 8c and a piston 8prigid with a ram 9. The cylinder 8c is fixed radially with respect tothe pivot 3g, on a side-member 10 of the vehicle frame.

In the second cylinder and ram unit 8 the chamber c having no ram andhaving the shape of a cylinder and the chamber a including the ram 9 andhaving an annular form are respectively connected by the hoses 11a, 11bto the companion chambers formed in the first cylinder 60 by the piston6p.

The free end of the piston ram 9 of the second cylinder 8 is formed inthe shape of a clevis having a small roller 9a which is engaged in agroove 12 of a plate in the shape of a sector 13, rigid with the crankarm 4g and extending perpendicularly to the axis of the correspondingwheel pivot 3g. The groove 12 has two parts 12d, 12g each formedsubstantially in the shape of the spiral of an arc substantiallycentered on the axis of the wheel pivot 33, the radii Rd, Rg of the endparts of these arcs being larger and respectively equal to each otherand the median radius Rm, obviously common to the two arcs, beingshorter as best seen in (FIG. 3).

The crank arms 4d, 4g are arranged parallel to each other when wheels1d, 1g are maintained parallel to each other and to wheels 2d, 2g formovement of the vehicle in a straight line; Under the effect of a stressof changed direction applied to wheels 1d, 13 (for example toward theleft, arrows f1, f2) the sector 13 is controlled by its pivot in orderto actuate, by means of the cam 12g, the cylinder 8 in the direction ofits shortening arrow 13 shown in FIG. 3.

The cylindrical chambers c and the annular chambers a of the secondcylinder and ram 8 and of the first cylinder and ram 6 constitute,together with hoses 11a, 11b two closed systems of constant volumeswhich are associated to each other by the pistons 8p, 6p. This ensuresmovements in opposite directions of these pistons in their cylinders. Inthis way, the shortening of the second cylinder and ram 8 causes anelongation (l is maximum) of the bar -7, the angular course alpha of thewheel 1g being thereby greater than the angular course beta of the wheel1d.

The power necessary for the above operation is a very small part of thepower applied manually to the steering wheel to ensure movement of thelinkage elements because this fraction of power must overcome only thefriction of the rams and the pistons in their cylinders and those of thefluids in the chambers a, c and the hoses 11a, 11b of the two closedsystems.

It is easy to choose, on the one hand, the arcs 12d, 12g of the cam 12 aprofile and, on the other hand, for the cylinders 6c and 80 sectionswhich ensure for each wheel orientation with respect to the direction ofrolling along a straight line, a common position G for the turningcenters of four wheels, which center is located (for all values that theangles alpha and beta may take) along the line m, n of the points ofcontact of the rear wheels 2d, 2g on the ground. Finally, it isindicated that in a turn the device permits a vehicle of the usual typeto take an orientation alpha of the inside: wheel which may greatlyexceed 60 and, of course, the cam arc (12g in FIG. 1) which correspondsto the inside angle of rotation" of the wheel pivot equipped with sector13 presents an angular opening equal'to the maximum value of saidanglealpha. The other wheel then presents an orientation beta and itwill be understood that the other cam arc l2 (12d in FIG. 1) is alsoequal to the maximum value of beta. In this way, turning to the rightwill cause utilization of the-arc 12d to ensure to the wheel lg anorientation beta toward the right, an elongation l of the bar 5-7 and anorientation alpha of the wheel id to the right.

Moreover, the linkage device described above is advantageouslyapplicable to an agricultural tractor due to the very small turningradii which it forms and to the safety of operation of said linkage, infact, with a view to clarification, it will be recalled that as shown in(FIG. 4) conventional self-propelled vehicles having a single rigidcoupling bar 5a present treads E of their wheel sets ld-2g, which are ofthe order of half the length of the wheelbase L of its wheels. For theposition for rolling in a straight line on all four wheels, the axes ofarm 4d, 4g converge to the middle Gm of the dis-.

tance between the rear wheels so that such a linkage permits maximumvalues of the turning angles alpha (inside wheel on the turn) lower than60. For such turns, the angle gamma" formed by arm 4g in this exampleand by the coupling bar 50 is of the order of 22, which is justsufficient to ensure good operation of the linkage.

As shown in (FIG. 5), this conventional linkage applied to a tractorhaving a relatively short frame of which the wheelbase L1 is of theorder of the size of its treads El does not permit wide turns, forexample of 50 or because the angle gamma mentioned above is then of theorder of 20 or 630 respectively, and the point of connection P of thebar 5a on the arm 4g is too close to its neutral position Pm.

There is obtained a substantial increase in the maximum turning anglealpha by adopting a parallel disposition of the arms 4d, 43 inaccordance with the form of embodiment shown in FIG. 1.

In addition, the coupling of two tractors having two steering wheels21d, 22d and 21g, 22g arranged in line (FIG. 6) a coupling bar 5b whichis shorter than the distance between the wheel pivots 3d, 3g causes adivergent disposition, with respect to the rear wheel set 2d, 23, of thearms 4d, 43, which further increases the maximum value of this anglealpha. The angles formed by the arm of the inside wheel on the turn andby the coupling bar are again equal to 30, which ensures good operationof the linkage.

The application of such an arrangement of arms 4d, 43 to the bar linkage5-7 of adjustable length described above, permits maximum turning valuesalpha at least equal to 90the angles gamma being again 2630, for pivot3d as well as for pivot 3g.

A tractor of the type shown in FIG. 6, employing this linkage permitspivoting about the point M situated in the middle of the frame of theelementary tractor arranged on the inside of a turn, which isadvantageous because it is possible to reduce the headlands formed bythe half turns at the ends of the rows of aligned plantations.

Shown in FIGS. 7 and 8 is an extensible coupling bar similar to bar 5-7of FIG. 1. This bar is constituted by a ram 5d connected at one end tothe crank arm 4d and rigid at its other end with the base of thecylinder of the first cylinder and ram 6d comprising a piston ram 7d,which piston ram 7d is connected to crank arm 4g. The minimum length ofsaid bar is practically equal to the distance between pivots 3d, 3g. Thepivot 33 of the steering wheel 1g being rigid with a crank arm 14 ofwhich the pivotal axis forms with the axis of the arm 4g an angle whichis slightly smaller than 90 (for example The piston ram 15 of the secondhydraulic cylinder and ram unit 16 is connected to this arm; the base ofthe cylinder 16c of said unit being rigid with a ram 17, the free end ofwhich is connected to the wheel pivot 3d.

The cylindrical chambers c and the annular chambers a of these twocylinder and ram units are connected to one another by flexible hoses180, 18c in order to form two systems of constant volumes associated bythe pistons of cylinder and rams 6d and 16.

Such a system of cylinder and rams 6d, 16 ensures fairly wide pivotingof the wheel on the inside of a turn; the precision of the orientationof wheels 1d, 1g is less efficient than that created by the cammechanism of FIG. 1, but the latter mechanism is more complicated andbulky than the tie-rod system of FIG. 7.

The securing of the ram 17 on the pivot 3d reduces as much as possibleorientation errors of wheels 1d, 1g at the start of the turn. The end ofram 17 may be mounted on another element of the vehicle frame.

It is clear that the replacement of units 6, 8 and 6d, 16 by unitshaving pistons with two rams would not modifiy the operational resultsdescribed above, since these piston rams would form an annular chamberin their respective cylinders.

What I claim is:

1. A steering linkage system for use with a vehicle having a frame andsteering ground supporting wheels therefor;

a pair of pivot means journaled on the frame and each rigid with theaxis of rotation of said steering ground supporting wheels;

21 pair of crank arms, one end of each of which is secured to each oneof said pivot means;

bar means having a first hydraulic cylinder pivotally connected to oneof its ends to the free end of one of said crank arms;

a piston within said first cylinder, said piston having a ram pivotallyconnected to its free end to the free end of the other of said pair ofcrank arms;

a second hydraulic cylinder connected by one of its ends to a fixedpoint of the frame;

a second piston within said second cylinder, said piston having a ramoperatively connected with at least one of the pivot means;

and fluid means connecting the chamber of the second cylinder withcorresponding chambers of said first cylinder to form two systems ofconstant volume.

2. A steering linkage system as claimed in claim 1 wherein the ram ofsaid second piston is operatively connected with at least one of thepivot means, by a plate rigid with said pivot means and having a groovein which is engaged a roller fixed to the end of the ram of the secondpiston.

3. A steering linkage system as claimed in claim 1, wherein said secondpiston is operatively connected with at least one of the pivot means bya crank arm axis angularly spaced to the geometrical axis of said secondcylinder.

4. A linkage system for steering the front wheels of a vehiclecomprising,

a pair of pivots journaled on frame elements of the vehicle and eachrigid with an axis of rotation of said front wheels,

a pair of crank arms respectively rigid with said pivots,

bar means engaged and maintained coaxially in sliding members andrespectively articulated by one of their ends to said crank arms,

a system of two hydraulic cylinders and rams connected to each other byflexible hoses to form two constant and closed volumes, the cylinder andram of one of said hydraulic cylinders and rams being associatedrespectively to said sliding members, and

means for coupling the second hydraulic cylinder and ram to one of saidpivots to ensure the operation of said second cylinder and ram under apivoting action of said pivot.

5. A steering linkage system as claimed in claim 4 wherein the twocoaxially arranged bar means form a coupling bar having a minimum lengthequal to or substantially shorter than the distance between the pivotson the frame elements of the vehicle.

6. A steering linkage as claimed in claim 5 wherein the coupling deviceof one of said cylinder and rams comprises a plate rigid with one ofsaid pivots and having a groove in which rides a roller rigid with theram of said second cylinder and ram.

7. A steering linkage as claimed in claim 4 wherein the coupling meansof said second cylinder and ram comprises a crank arm rigid with one ofthe pivots and on which is articulated one of the parts of said secondcylinder and ram.

8. A steering linkage as claimed in claim 7, wherein the other part ofsaid second cylinder and ram is attached by means of an articulation tothe other pivot.

1. A steering linkage system for use with a vehicle having a frame andsteering ground supporting wheels therefor; a pair of pivot meansjournaled on the frame and each rigid with the axis of rotation of saidsteering ground supporting wheels; a pair of crank arms, one end of eachof which is secured to each one of said pivot means; bar means having afirst hydraulic cylinder pivotally connected to one of its ends to thefree end of one of said crank arms; a piston within said first cylinder,said piston having a ram pivotally connected to its free end to the freeend of the other of said pair of crank arms; a second hydraulic cylinderconnected by one of its ends to a fixed point of the frame; a secondpiston within said second cylinder, said piston having a ram operativelyconnected with at least one of the pivot means; and fluid meansconnecting the chamber of the second cylinder with correspondingchambers of said first cylinder to form two systems of constant volume.2. A steering linkage system as claimed in claim 1 wherein the ram ofsaid second piston is operatively connected with at least one of thepivot means, by a plate rigid with said pivot means and having a groovein which is engaged a roller fixed to the end of the ram of the secondpiston.
 3. A steering linkage system as claimed in claim 1, wherein saidsecond piston is operatively connected with at least one of the pivotmeans by a crank arm axis angularly spaced to the geometrical axis ofsaid second cylinder.
 4. A linkage system for steering the front wheelsof a vehicle comprising, a pair of pivots journaled on frame elements ofthe vehicle and each rigid with an axis of rotation of said frontwheels, a pair of crank arms respectively rigid with said pivots, barmeans engaged and maintained coaxially in sliding members andrespectively articulated by one of their ends to said crank arms, asystem of two hydraulic cylinders and rams connected to each other byflexible hoses to form two constant and closed volumes, the cylinder andram of one of said hydraulic cylinders and rams being associatedrespectively to said sliding members, and means for coupling the secondhydraulic cylinder and ram to one of said pivots to ensure the operationof said second cylinder and ram under a pivoting action of said pivot.5. A steering linkage system as claimed in claim 4 wherein the twocoaxially arranged bar means form a coupling bar having a minimum lengthequal to or substantially shorter than the distance between the pivotson the frame elements of the vehicle.
 6. A steering linkage as claimedin claim 5 wherein the coupling device of one of said cylinder and ramscomprises a plate rigid with one of said pivots and having a groove inwhich rides a roller rigid with the ram of said second cylinder and ram.7. A steering linkage as claimed in claim 4 wherein the coupling meansof said second cylinder and ram comprises a crank arm rigid with one ofthe pivots and on which is articulated one of the parts of said secondcylinder and ram.
 8. A steering linkage as claimed in claim 7, whereinthe other part of said second cylinder and ram is attached by means ofan articulation to the other pivot.